The invention relates to the determination of port identities in a telecommunications system and, in particular to the automatic determination of port identities in a heterogenous telecommunications system.
In 1876, inside a third floor walk-up garret apartment in the Scollay Square section of Boston Massachusetts, Alexander Graham Bell spoke the first sentence transmitted over telephone wires. Technical innovations have dramatically transformed the telecommunications industry over the past one hundred and twenty three years. For example, telecommunications switching systems have evolved considerably from xe2x80x9chand operatedxe2x80x9d systems in which one instrument was electrically connected (through a hierarchical switching network) to another through the intervention of a human operator who would physically plug one circuit into another. Such direct electrical connection of two or more channels between two points (at least one channel in each direction), a connection that provides a user with exclusive use of the channels to exchange information, is referred to as circuit switching, or line switching. Human operators have largely been replaced by systems which employ electronic switching systems (ESS), in which the instruments are automatically connected through the network by electronic systems.
Additionally, in many cases, the signalling system employs optical signalling instead of, or in addition to, electronic signalling. Nevertheless, such switching systems often still employ circuit switching, a technique which yields highly reliable service, particularly for such xe2x80x9creal timexe2x80x9d communications applications as voice, in which the momentary loss of a channel is annoying and repeated such losses are unacceptable. Switching systems may interconnect telephone instruments through circuit switching, employing time division multiplexing (TDM), for example. The switching system may carry digitized telecommunications signal over optical paths that are in conformity with synchronous optical network (SONET) standards. Such networks include network elements such as SONET network elements, SDH network elements, or wavelength division multiplexed network elements, for example. Circuit switching network elements include any network elements which conforms with SONET/SDH digital signal formats. The signal formats are described, for example, in a Technical Advisory entitled xe2x80x9cSynchronous Optical Network (SONET) Transport Systems: Common Generic Criteriaxe2x80x9d, TA-NWT-000253, Bell Communications Research, Issue Sep. 6, 1990, which is hereby incorporated by reference. For a variety of reasons it may be important to know which port in a given network element (NE) within such a system is connected to a particular port of another NE within the system.
Although SONET systems may incorporate a facility for such port identification and network elements within a circuit switching telecommunications system may employ this facility to identify ports, network elements within a packet switching system do not typically provide for port identification. That is, a technique known as packet switching may be employed for the transmission of data over telecommunications network. With packet switching data is transmitted in packets, and the communications channel is only occupied for the duration of a packet""s transmission. After the transmission, the channel is available for use by other packets being transferred for other users. The packetized transmission may be transmitted using asynchronous transfer mode (ATM) techniques, for example. Asynchronous transfer mode (ATM) is a connection-oriented transmission technique that employs fixed-size blocks of data, called cells, each of which consists of a five octet long header and an information field that is forty-eight octets long. Packet switching network elements, such as ATM nodes or Internet Protocol (IP) routers, typically ignore the SONET signalling that might otherwise be employed to identify specific interconnected ports within a telecommunications network. Consequently, operator intervention may be required to accomplish such identification. Such a process would be time consuming, fraught with the potential for errors, and cost-prohibitive. Systems that employ both circuit switching and packet switching network elements and which employ SONET signalling may be referred to hereinafter as heterogeneous telecommunications systems. A heterogeneous telecommunications system that provides for automatic port identification would therefore be highly desirable.
A heterogeneous telecommunications system in accordance with the principles of the present invention employs xe2x80x9cout of bandxe2x80x9d signalling to automatically discover the identities of ports interconnected between packet switching and circuit switching network elements. Interconnected circuit switching and packet switching network elements employ a network management channel, such as a local area network (LAN) network management link, to automatically discover port binding information (that is, which port of an initiating network element is connected to which port of a receiving network element).
In accordance with the principles of the present invention, an NE may, under various circumstances, such as it""s initialization, or re-booting, initiate a port interconnectivity discovery process by sending a recognition request message to a network element to which it is bound through a network link. The recognition request message is transmitted from the initiating network element to the receiving network element through an xe2x80x9cout of band channelxe2x80x9d, such as a network management link, which may take the form of a LAN, for example. The initiating network element awaits an acknowledgement signal from the receiving network element and, once received, transmits a test message from a specific port to the receiving network element. The test message transmitted by the initiating network element may be transport level overhead message, such as a SONET/SDH xe2x80x9cK2 bytexe2x80x9d protection message, for example. After sending the, acknowledgement message to the initiating network element, the receiving network element begins polling its ports to detect which port receives the test message. Once the receiving network element detects which of its ports receives the test message, the receiving network element records the port binding information and stops its own ports. Additionally, the receiving network element transmits a detection message to the initiating network element, which includes the receiving network element""s port identity, through the out of band channel. Upon receiving the detection message from the receiving network element, the initiating network element stops sending the test message through the SONET/SDH link, records the port binding information, and transmits a recognition acknowledgement message to the receiving network element through the out of band channel.